[FFmpeg-devel] looking to hire expert for a short project: lossless screen and sound capture 4k@60hz

[FFmpeg-devel] looking to hire expert for a short project: lossless screen and sound capture 4k@60hz

[Misha Aizatulin]

Hi all,

   I've been directed here from https://ffmpeg.org/consulting.html as I'm looking to hire an expert 
for what should hopefully be a simple but well-paid job. Please let me know if anyone has availability!

   What I'm trying to do is capture demoscene demos in full quality: 4k@60hz (with sound of course). 
My rig is presentable: nvidia A6000 and 192G RAM. I am a software engineer, but don't know very much 
about video processing or ffmpeg.

   I tried:
ffmpeg -filter_complex ddagrab=0,hwdownload,format=bgra,framerate=60 -c:v utvideo output.mkv

   What happened: the first minute or so (always roughly the same length of time) is captured fine. 
Then it drops off the cliff, something like 1 frame per 3 seconds, but also trying to interpolate 
between them, so it looks really weird.

   I was not able to get ffmpeg to report to me any dropped frames which is upsetting and worrying. 
I also don't understand where the interpolation comes from and would love to turn it off.

   I can't think of a reason for the droppage: my RAM is big enough to hold the full video (about 
50G total). My only theory is that GPU memory might be getting full (will check tomorrow), but I'd 
expect hwdownload rates to not be that slow.

   Maybe I should use hevc_nvenc with lossless setting, but there's some talk about the yuv420 
conversion being not lossless...

   Anyway, would really appreciate someone educating me on these and would happily pay for your time!

Best,
   Misha
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Re: [FFmpeg-devel] looking to hire expert for a short project: lossless screen and sound capture 4k@60hz

[Tomas Härdin]

fre 2023-07-28 klockan 02:49 +0100 skrev Misha Aizatulin:
> Hi all,
> 
>    I've been directed here from https://ffmpeg.org/consulting.html as
> I'm looking to hire an expert 
> for what should hopefully be a simple but well-paid job. Please let
> me know if anyone has availability!
> 
>    What I'm trying to do is capture demoscene demos in full quality:
> 4k@60hz (with sound of course). 
> My rig is presentable: nvidia A6000 and 192G RAM. I am a software
> engineer, but don't know very much 
> about video processing or ffmpeg.
> 
>    I tried:
> ffmpeg -filter_complex ddagrab=0,hwdownload,format=bgra,framerate=60
> -c:v utvideo output.mkv
> 
>    What happened: the first minute or so (always roughly the same
> length of time) is captured fine. 
> Then it drops off the cliff, something like 1 frame per 3 seconds,
> but also trying to interpolate 
> between them, so it looks really weird.
> 
>    I was not able to get ffmpeg to report to me any dropped frames
> which is upsetting and worrying. 
> I also don't understand where the interpolation comes from and would
> love to turn it off.
> 
>    I can't think of a reason for the droppage: my RAM is big enough
> to hold the full video (about 
> 50G total). My only theory is that GPU memory might be getting full
> (will check tomorrow), but I'd 
> expect hwdownload rates to not be that slow.
> 
>    Maybe I should use hevc_nvenc with lossless setting, but there's
> some talk about the yuv420 
> conversion being not lossless...
> 
>    Anyway, would really appreciate someone educating me on these and
> would happily pay for your time!

I would suggest using .kkapture: http://farbrausch.de/~fg/kkapture/

/Tomas
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Re: [FFmpeg-devel] looking to hire expert for a short project: lossless screen and sound capture 4k@60hz

[Misha Aizatulin]

> I would suggest using .kkapture: http://farbrausch.de/~fg/kkapture/

   Interesting - I haven't tried .kkapture because I thought that it only works for demos that are 
using the API as of when the tool was created - which means a lot of the newer demos won't work with 
it. But maybe I'm wrong? I'll poke around.

   I tried Capturinha (https://github.com/kebby/Capturinha), but couldn't make it work for lossless 
- it might be an easy code change though.

   I also tried OBS and almost succeeded. The only remaining problem with OBS is the colour space 
conversion which is not lossless. More precisely, trying NV12 gives me wrong colours and trying 
anything else gives me "Encoding Overloaded" for no apparent reason (all performance indicators, CPU 
and GPU look mild).

 >> My only theory is that GPU memory might be getting full

   I checked, it wasn't.

 >> Maybe I should use hevc_nvenc with lossless setting

   Tried, ran into the same problem as with hwdownload->utvideo. Maybe something about the grabber?
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Re: [FFmpeg-devel] looking to hire expert for a short project: lossless screen and sound capture 4k@60hz

[Misha Aizatulin]

>    Interesting - I haven't tried .kkapture because I thought that it only works for demos that are 
> using the API as of when the tool was created - which means a lot of the newer demos won't work with 
> it. But maybe I'm wrong? I'll poke around.

   Indeed. I tried running kkapture on a demo from 2005 and it worked fine, but a more recent demo 
fails with "startup instrumentation failed".
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